linux-kernel - [PATCH 7/7] sched/uclamp: Cater for uclamp in find_energy_efficient

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Date:   Wed, 29 Jun 2022 20:46:32 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Ingo Molnar <mingo@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     linux-kernel@...r.kernel.org, Xuewen Yan <xuewen.yan94@...il.com>,
        Wei Wang <wvw@...gle.com>,
        Jonathan JMChen <Jonathan.JMChen@...iatek.com>,
        Hank <han.lin@...iatek.com>, Qais Yousef <qais.yousef@....com>
Subject: [PATCH 7/7] sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition

If the utilization of the woken up task is 0, we skip the energy
calculation because it has no impact.

But if the task is boosted (uclamp_min != 0) will have an impact on task
placement and frequency selection. Only skip if the util is truly
0 after applying uclamp values.

Change uclamp_task_cpu() signature to avoid unnecessary additional calls
to uclamp_eff_get(). feec() is the only user now.

Fixes: 732cd75b8c920 ("sched/fair: Select an energy-efficient CPU on task wake-up")
Signed-off-by: Qais Yousef <qais.yousef@....com>
---
 kernel/sched/fair.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 499ef7a7288c..a112ca45864c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4057,14 +4057,16 @@ static inline unsigned long task_util_est(struct task_struct *p)
 }
 
 #ifdef CONFIG_UCLAMP_TASK
-static inline unsigned long uclamp_task_util(struct task_struct *p)
+static inline unsigned long uclamp_task_util(struct task_struct *p,
+					     unsigned long uclamp_min,
+					     unsigned long uclamp_max)
 {
-	return clamp(task_util_est(p),
-		     uclamp_eff_value(p, UCLAMP_MIN),
-		     uclamp_eff_value(p, UCLAMP_MAX));
+	return clamp(task_util_est(p), uclamp_min, uclamp_max);
 }
 #else
-static inline unsigned long uclamp_task_util(struct task_struct *p)
+static inline unsigned long uclamp_task_util(struct task_struct *p,
+					     unsigned long uclamp_min,
+					     unsigned long uclamp_max)
 {
 	return task_util_est(p);
 }
@@ -6913,7 +6915,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 	target = prev_cpu;
 
 	sync_entity_load_avg(&p->se);
-	if (!task_util_est(p))
+	if (!uclamp_task_util(p, p_util_min, p_util_max))
 		goto unlock;
 
 	for (; pd; pd = pd->next) {
-- 
2.25.1